This invention relates to packaging materials suitable for heating food items in a microwave oven. In particular it relates to materials and processes for preparation of food items characterized by varying configurations and requiring surface browning and crisping.
Many food products are difficult to prepare in a microwave oven, particularly those that require surface browning and crisping. In order to provide such browning and crisping, the use of packaging materials containing microwave susceptors has become popular. Such susceptors absorb microwave energy and as a result generate heat. Under favorable conditions the susceptors transfer sufficient heat to the adjacent food surfaces to create a browning and crisping effect.
U.S. Pat. No. 4,641,005, Seiferth, discloses a disposable food receptacle for use in microwave cooking, which includes a provision to brown the exterior of the food in the receptacle. A thin layer of an electrically conductive material is incorporated into the receptacle on the food contacting surfaces thereof, so that the conductive layer will become heated by the microwave radiation and will, in turn, brown the exterior of the food in the receptacle. The receptacle includes a smooth surfaced plastic film, as a protective layer, and a support means formed of paper stock material.
U.S. Pat. No. 4,230,924, Brastad, discloses a food package including a flexible wrapping sheet of dielectric material capable of conforming to at least a portion of the article of food's shape. The dielectric wrapping sheet has a flexible metallic coating thereon, the coating being subdivided into a number of individual metallic islands or pads separated by criss-crossing non-metallic gaps.
U.S. Pat. No. 4,267,420, Brastad, discloses a food item wrapped with plastic film having a very thin coating thereon. The film conforms to a substantial portion of the food item. The coating converts some of the microwave energy into heat which is transmitted directly to the surface portion of the food so that a browning and/or crispening is achieved.
U.S. Pat. No. 4,518,651, Wolfe, discloses a flexible composite material which exhibits a controlled absorption of microwave energy based on presence of particulate carbon in a polymeric matrix bound to a porous substrate. The coating is pressed into the porous substrate using specified temperatures, pressures, and times, resulting in improved heating.
Copending U.S. application No. 002,980 describes a conformable wrap for microwave cooking, comprising a dielectric substrate substantially transparent to microwave radiation and a coating on at least one surface of the substrate comprising about 5 to 80% by weight of metal or metal alloy susceptor in flake form, and about 95 to 20% by weight of a thermoplastic dielectric matrix. An aluminum flake of selected geometry is preferred.
Copending U.S. application No. 037,988, now U.S. Pat. No. 4,833,007 discloses a flexible wrap with a susceptor material which couples to both the electrical and magnetic components of the microwave field. One such film comprises stainless steel sputtered onto polyethylene terephthalate film.
Copending U.S. application No. 188,556 discloses a conformable laminated wrap for packaging articles of food requiring browning and crispening and a degree of shielding during microwave cooking. The laminated wrap has at least two layers of heat resistant microwave transparent plastic film, and at least one substantially continuous layer of microwave susceptive material, which is coated on at least one of the interior surfaces or interfaces formed between the plastic films of the laminate.
It is also known in the art to simulate a natural product by forming a food precursor in a mold to achieve a final product of appropriate texture and appearance. For example, uniform reconstituted potato chips are sold commercially, nested and packed in a compact container. It is believed that for formation of such potato chips, a dehydrated potato powder is hydrated and conventionally baked in molds to produce browned and crisped chips of uniform size.